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We show that the sex of human experimenters affects mouse behaviors and responses following administration of the rapid-acting antidepressant ketamine and its bioactive metabolite (2R,6R)-hydroxynorketamine. Mice showed aversion to the scent of male experimenters, preference for the scent of female experimenters and increased stress susceptibility when handled by male experimenters. This human-male-scent-induced aversion and stress susceptibility was mediated by the activation of corticotropin-releasing factor (CRF) neurons in the entorhinal cortex that project to hippocampal area CA1. Exposure to the scent of male experimenters before ketamine administration activated CA1-projecting entorhinal cortex CRF neurons, and activation of this CRF pathway modulated in vivo and in vitro antidepressant-like effects of ketamine. A better understanding of the specific and quantitative contributions of the sex of human experimenters to study outcomes in rodents may improve replicability between studies and, as we have shown, reveal biological and pharmacological mechanisms.

Modulation of the endocannabinoid system (ECS) is a novel putative target for therapeutic intervention in depressive disorders. Altering concentrations of one of the principal endocannabinoids, N-arachidonoylethanolamine, also known as anandamide (AEA) can affect depressive-like behaviors through several mechanisms including anti-inflammatory, hormonal, and neural circuit alterations. Recently, isoflavonoids, a class of plant-derived compounds, have been of therapeutic interest given their ability to modulate the metabolism of the endogenous ligands of the ECS. To determine the therapeutic potential of isoflavonoids, we screened several candidate compounds (Genistein, Biochanin-A, and 7-hydroxyflavone) in silico to determine their binding properties with fatty acid amide hydrolase (FAAH), the primary degrative enzyme for AEA. We further validated the ability of these compounds to inhibit FAAH and determined their effects on depressive-like and locomotor behaviors in the forced swim test (FST) and open field test in male and female mice. We found that while genistein was the most potent FAAH inhibitor, 7-hydroxyflavone was most effective at reducing immobility time in the forced swim test. Finally, we measured blood corticosterone and prefrontal cortex AEA concentrations following the forced swim test and found that all tested compounds decreased corticosterone and increased AEA, demonstrating that isoflavonoids are promising therapeutic targets as FAAH inhibitors.

Hydroxynorketamines (HNKs) are formed in vivo after (R,S)-ketamine (ketamine) administration. The 12 HNK stereoisomers are distinguished by the position of cyclohexyl ring hydroxylation (at the 4, 5, or 6 position) and their unique stereochemistry at two stereocenters. Although HNKs were initially classified as inactive metabolites because of their lack of anesthetic effects, more recent studies have begun to reveal their biologic activities. In particular, (2R,6R)- and (2S6)-HNK exert antidepressant-relevant behavioral and physiologic effects in preclinical models, which led to a rapid increase in studies seeking to clarify the mechanisms by which HNKs exert their pharmacological effects. To date, the majority of HNK research has focused on the actions of (2R,6R)-HNK because of its robust behavioral actions in tests of antidepressant effectiveness and its limited adverse effects. This review describes HNK pharmacokinetics and pharmacodynamics, as well as the putative cellular, molecular, and synaptic mechanisms thought to underlie their behavioral effects, both following their metabolism from ketamine and after direct administration in preclinical studies. Converging preclinical evidence indicates that HNKs modulate glutamatergic neurotransmission and downstream signaling pathways in several brain regions, including the hippocampus and prefrontal cortex. Effects on other neurotransmitter systems, as well as possible effects on neurotrophic and inflammatory processes, and energy metabolism, are also discussed. Additionally, the behavioral effects of HNKs and possible therapeutic applications are described, including the treatment of unipolar and bipolar depression, post-traumatic stress disorder, chronic pain, neuroinflammation, and other anti-inflammatory and analgesic uses. Significance Statement Preclinical studies indicate that hydroxynorketamines (HNKs) exert antidepressant-relevant behavioral actions and may also have analgesic, anti-inflammatory, and other physiological effects that are relevant for the treatment of a variety of human diseases. This review details the pharmacokinetics and pharmacodynamics of the HNKs, as well as their behavioral actions, putative mechanisms of action, and potential therapeutic applications.

Differential rodent responses to the sex of human experimenters could have far reaching consequences in preclinical studies. Here, we show that the sex of human experimenters affects mouse behaviours and responses to the rapid-acting antidepressant ketamine and its bioactive metabolite (2R,6R)-hydroxynorketamine. We found that mice manifest aversion to human male odours, preference to female odours, and increased susceptibility to stress when handled by male experimenters. This male induced aversion and stress susceptibility is mediated by the activation of brain corticotropin-releasing factor (CRF) neurons projecting from the entorhinal cortrex to hippocampal area CA1. We further establish that exposure to male scent prior to ketamine administration activates CRF neurons projecting from the entorhinal cortex to hippocampus, and that CRF is necessary and sufficient for ketamine’s in vivo and in vitro actions. Further understanding of the specific and quantitative contributions of the sex of human experimenters to different experimental outcomes in rodents may lead not only to reduced heterogeneity between studies, but also increased capability to uncover novel biological mechanisms.

In susceptible populations, stress is a major risk factor for the development of mental disorders, including depression. Estradiol, often considered a female hormone, is distributed in the male brain via aromatization of testosterone. The role of estrogen receptors (ERs) in male stress susceptibility and depression is not well understood. We found that absence of ERβ is associated with susceptibility to stress in male mice and that activity of ERβ-projecting neurons from the basolateral amygdala to nucleus accumbens is reduced in hypogonadal mice subjected to stress, while activation of this circuit reverses stress-induced maladaptive behaviors. We identified that absence of estradiol, but not testosterone per se, underlies stress susceptibility and that brain-selective delivery of estradiol prevents the development of depression-related behaviors. Our findings provide evidence for an estrogen-based mechanism underlying stress susceptibility and offer an unexpected therapeutic strategy for treating depression in males.

An early inflammatory insult is the most recognized risk factor associated with neurodevelopmental psychiatric disorders, even more so than genetic variants. Notably, complement component 4 (C4), a molecule involved in inflammatory responses, has been strongly associated with schizophrenia (SZ) and its role in other neurodevelopmental disorders, such as autism (ASD), is an area of active investigation. However, while C4 in SZ has been implicated in the context of synaptic pruning, little is known about its neuroinflammatory role. The subventricular zone (SVZ) is a region heavily involved in neurodevelopment and neuroimmune interactions through the lifespan; thus, it is a region wherein C4 may play a vital role in disease pathology. Using in situ hybridization with radioactive riboprobes and RNAscope, we identified robust astrocytic expression of C4 in the SVZ and in the septum pellucidum. C4 was also expressed in ependyma, neurons, and Ki67

Objective Childhood maltreatment (CM) is a public health crisis that results in negative physical, mental health, and psychosocial (e.g., resource attainment) outcomes. Resource attainment is a critical outcome for marginalized populations, such as low-income African American women. This study addresses the gap in the literature regarding the association between CM and effectiveness of resource attainment and the potential mediating role of self-esteem in this association for African American women. Method Data were gathered from a large public inner-city, university-affiliated health care system in the Southeastern United States. Participants selected were low-income African American women who have experienced intimate partner violence (IPV) and have attempted suicide in the prior year. The participants for this study completed the Childhood Trauma Questionnaire, the Beck Self-Esteem Scale, and the Effectiveness in Obtaining Resources Scale. Results Mediation analyses using bootstrapping with 213 women revealed the powerful role self-esteem plays in explaining the link between CM and resource attainment in low-income African American women. Specifically, overall CM and four of its subtypes (emotional abuse, physical abuse, emotional neglect, and physical neglect) were all associated with decreased resource attainment via the effect of decreased self-esteem. Sexual abuse was the only subtype of CM not significantly associated with self-esteem nor effectiveness of resource attainment. Conclusion This research highlights the importance of screening for CM, its subtypes, and resource attainment in this population and bolstering self-esteem through psychological interventions to increase women's capacity to effectively secure necessary community resources. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

A 33-year-old previously healthy Middle Eastern male presented to the emergency department with four weeks of progressively worsening fatigue, dyspnea on exertion, night sweats, and a 10-pound weight loss after suffering a self-limiting viral upper respiratory illness. He was found to be profoundly anemic and thrombocytopenic with normal white blood cell count with a lymphocytic predominance. His anemia was refractory to red blood cell transfusions, to which he developed hyperbilirubinemia. A CT scan revealed hepatomegaly and massive splenomegaly associated with multi-station abdominopelvic lymphadenopathy. A peripheral blood smear revealed several lymphocytes with hairy cell features and bone marrow biopsy revealed hypercellularity with interstitial infiltration by mature lymphoid cells. Flow cytometry confirmed the diagnosis of hairy cell leukemia (HCL) and this patient was initiated on cladribine chemotherapy. This case illustrates the uniqueness of this patient presenting within a short time course, at an atypical age, and with uncommon features for HCL including lymphadenopathy, hepatomegaly, and petechial skin rash. This case also highlights an important point regarding the management of severe anemia in the acute setting while undergoing splenic sequestration. His lack of response to red blood cell transfusions highlights the need for more research on the use of transfusions in patients who are not current surgical candidates for splenectomy.

Maternal immune activation (MIA) with the viral mimic poly I:C provides an established rodent model for studying schizophrenia (SZ) and other human neurodevelopmental disorders. Postnatal infections are additional risk factors in SZ and may cumulatively contribute to the emergence of pathophysiology. Underlying mechanisms may involve metabolites of the kynurenine pathway (KP) of tryptophan degradation, which is readily induced by inflammatory stimuli. Here we compared the expression of selected cytokines and KP enzymes, and the levels of selected KP metabolites, in the brain of MIA offspring following a second, acute immune challenge with lipopolysaccharides (LPS) on postnatal day (PND) 35 (adolescence) or PND 60 (early adulthood). Assessed in adolescence, MIA did not alter the expression of pro-inflammatory cytokines (except TNF-α) or KP metabolite levels compared to controls, but substantially reduced the expression of the anti-inflammatory cytokines IL-4 and IL-10 and influenced the expression of two of the four KP enzymes examined (IDO1 and TDO2). LPS treatment caused distinct changes in the expression of pro- and anti-inflammatory cytokines, as well as KP enzymes in MIA offspring, but had no effect on KP metabolites compared to control rats. Several of these effects were blunted in MIA offspring receiving LPS on PND 60. Notably, LPS caused a significant reduction in brain kynurenine levels in these animals. Of relevance for SZ-related hypotheses, these results indicate that MIA leads to an increasingly defective, rather than an overactive, immune regulation of cerebral KP metabolism during the postnatal period.

The recent spread of Zika virus (ZIKV) and its association with congenital defects and neurological disorders has created an urgent need to understand the pathogenesis of ZIKV and identify therapeutic strategies that will prevent or eliminate them. The neurodevelopmental defects associated with ZikV infections early in pregnancy are well documented, however the potential defects associated with infections in late pregnancy and perinatal period are less well characterized. Further, the long-term sequelae of these infections are not fully understood. Immunocompetent C57BL/6 mice infected at one day old (P1), which neurodevelopmentally model late pregnancy in humans, develop a transient neurological syndrome including unsteady gait, kinetic tremors, severe ataxia and seizures 10-15 days post-infection (dpi) but symptoms subside after a week, and most animals survive. Despite apparent recovery, MRI of convalescent mice shows reduced cerebellar volume that correlates with altered coordination and motor function as well as hyperactivity and impulsivity. Persistent mRNA levels of pro-inflammatory genes including Cd80, Il-1α, and Ifn-γ together with Cd3, Cd8 and perforin (PrfA), suggested the persistence of a low-grade inflammatory process. Further, the brain parenchyma of convalescent mice harbor multiple small foci with viral antigen, active apoptotic processes in neurons, and cellular infiltrates, surrounded by activated astrocytes and microglia as late as 1-year post-infection. Detection of negative-sense strand viral RNA and replication of virus derived from these convalescent mice by blinded passage in Vero cells confirmed that low levels of live ZikV persist in CNS of convalescent mice life-long. Our studies establish that Zika can establish reservoirs in CNS and suggest that anti-viral treatment that clears virus from the CNS as well as long-term neurological and behavioral monitoring may be needed for patients known to be exposed to ZikV at an early age.Author’s summaryThe congenital brain malformations associated with ZikV infections early in pregnancy are well documented, however whether apparently asymptomatic perinatal exposure could lead to long term sequelae is not fully understood. Using a non-lethal neonatal mouse model, we examine host-pathogen interactions, anatomical changes and behavioral patterns by following survivors of the acute infection for over 1 year. We discover that infectious Zika virus has the potential to remain in the CNS for life, lodged within small foci surrounded by gliosis and infiltrating immune cells that may act to limit the viral spread, but also interfere with healing and contribute to life-long neuropathic and behavioral sequelae. These results suggest that anti-viral treatment and long-term neurological and behavioral monitoring may be indicated for patients known to have been exposed to Zika virus, regardless of neurodevelopmental disease severity.

Psychological stress is known to have profound effects on immune function and to promote inflammatory conditions. Elevated circulating levels of cytokines associated with stress are known to increase the risk to several diseases, but little is known about this mechanism. This study assessed the role of T cells on cytokine levels after exposure to stress in the learned helplessness paradigm. Adoptive transfer of CD4+ T cells into Rag2-/- mice did not change cytokine levels to stress while CD8+ T cells resulted in an increase in TNF-α, IL-6 and IFN-γ in stressed Rag2-/- mice. Moreover, depletion of CD8+ T cells in WT mice abolished these cytokine responses to stress. Corticosterone and behavioral stress responsiveness was impaired in Rag2-/- mice reconstituted with CD8+ T cells. Notably, depletion of these cells in WT mice had no effect on behavior or corticosterone levels. Exposure to stress did not change the expression of canonical markers of T cell activation including CD62L and CD44 or modified intracellular cytokine content, suggesting that they are not the main producers of circulating cytokines in response to stress. These results show that CD8+ T cells promote TNF-α, IL-6 and IFN-γ responses to stress, possibly by stimulating non-lymphoid cells.

Immunological abnormalities are increasingly reported in people with schizophrenia, but no clear functional biomarkers associated with genetic correlates of the disease have been found. Regulatory T cells (Tregs) are key immunoregulatory cells involved in the control of inflammatory processes and their functions are directly related to the human leucocyte antigen (HLA) gene, which has been implicated in schizophrenia genetic studies. However, there is a lack of studies reporting Treg status in people with schizophrenia. In the current study, the proportion of circulating Tregs was examined using flow cytometry in 26 medicated participants with schizophrenia and 17 healthy controls. Psychiatric symptoms and cognitive function were evaluated using the Scale for the Assessment of Negative Symptoms, the Brief Psychiatric Rating Scale, and the MATRICS Consensus Cognitive Battery. The proportion of Tregs was found to be significantly greater in the schizophrenia group compared to healthy controls. No differences were observed in total lymphocyte counts or CD3(+) and CD4 (+) T cells, confirming a specific effect for Tregs. Elevated Tregs in schizophrenia correlated with fewer negative symptoms, a core domain of the illness. These results suggest that Tregs may contribute to improved negative symptoms in schizophrenia, possibly by counteracting on-going inflammatory processes.

The concept of the brain as an immune privileged organ is rapidly evolving in light of new findings outlining the sophisticated relationship between the central nervous and the immune systems. The role of T cells in brain development and function, as well as modulation of behavior has been demonstrated by an increasing number of studies. Moreover, recent studies have redefined the existence of a brain lymphatic system and the presence of T cells in specific brain structures, such as the meninges and choroid plexus. Nevertheless, much information is needed to further the understanding of brain T cells and their relationship with the central nervous system under non-inflammatory conditions. In the present study we employed the Rag2(-/-) mouse model of lymphocyte deficiency and reconstitution by adoptive transfer to study the temporal and anatomical expansion of T cells in the brain under homeostatic conditions. Lymphopenic Rag2(-/-) mice were reconstituted with 10 million lymphoid cells and studied at one, two and four weeks after transfer. Moreover, lymphoid cells and purified CD4(+) and CD8(+) T cells from transgenic GFP expressing mice were used to define the neuroanatomical localization of transferred cells. T cell numbers were very low in the brain of reconstituted mice up to one week after transfer and significantly increased by 2weeks, reaching wild type values at 4weeks after transfer. CD4(+) T cells were the most abundant lymphocyte subtype found in the brain followed by CD8(+) T cells and lastly B cells. Furthermore, proliferation studies showed that CD4(+) T cells expand more rapidly than CD8(+) T cells. Lymphoid cells localize abundantly in meningeal structures, choroid plexus, and circumventricular organs. Lymphocytes were also found in vascular and perivascular spaces and in the brain parenchyma across several regions of the brain, in particular in structures rich in white matter content. These results provide proof of concept that the brain meningeal system, as well as vascular and perivascular spaces, are homing sites of lymphocytes and suggest the possibility of a brain specific T cell subtype.

Accumulating evidence supports a role of T cells in behavioral stress responsiveness. Our laboratory previously reported that lymphocyte deficient Rag2(-/-) mice on a BALB/c background display resilience to maladaptive stress responses when compared with immune competent mice in the predator odor exposure (POE) paradigm, while exhibiting similar behavior in a cued fear-conditioning (FC) paradigm. In the present study, Rag2(-/-) mice on a C57BL/6 background were assessed in the same behavioral paradigms, as well as additional tests of anxiety and depressive-like behavior. Furthermore, the effects of naïve CD4(+ ) T cells were evaluated by adoptive transfer of functional cells from nonstressed, wild-type donors to Rag2(-/-) mice. Consistent with our prior results, Rag2(-/-) mice displayed an attenuated startle response after POE. Nevertheless, reconstitution of Rag2(-/-) mice with CD4(+ ) T cells did not modify startle reactivity. Additionally, in contrast with our previous findings, Rag2(-/-) mice showed attenuated fear responses in the FC paradigm compared to wild-type mice and reconstitution with CD4(+ ) T cells promoted fear learning and memory. Notably, reconstitution with CD4(+ ) T cells had anxiolytic and antidepressant-like effects in Rag2(-/-) mice that had not been previously stressed, but had no effect after POE. Taken together, our results support a role of CD4(+ ) T cells in emotionality, but also indicate that they may promote fear responses by enhancing learning and memory processes.

Psychological stress is known to have profound effects on immune function and to promote inflammatory conditions. Elevated circulating levels of cytokines associated with stress are known to increase the risk to several diseases, but little is known about this mechanism. This study assessed the role of T cells on cytokine levels after exposure to stress in the learned helplessness paradigm. Adoptive transfer of CD4(+) T cells into Rag2(−/−) mice did not change cytokine levels to stress while CD8(+) T cells resulted in an increase in TNF-α, IL-6 and IFN-γ in stressed Rag2(−/−) mice. Moreover, depletion of CD8(+) T cells in WT mice abolished these cytokine responses to stress. Corticosterone and behavioral stress responsiveness was impaired in Rag2(−/−) mice reconstituted with CD8(+) T cells. Notably, depletion of these cells in WT mice had no effect on behavior or corticosterone levels. Exposure to stress did not change the expression of canonical markers of T cell activation including CD62L and CD44 or modified intracellular cytokine content, suggesting that they are not the main producers of circulating cytokines in response to stress. These results show that CD8(+) T cells promote TNF-α, IL-6 and IFN-γ responses to stress, possibly by stimulating non-lymphoid cells.

Inflammatory diseases are highly associated with affective disorders including depression and anxiety. While the role of the innate immune system on emotionality has been extensively studied, the role of adaptive immunity is less understood. Considering that chronic inflammatory conditions are mediated largely by maladaptive lymphocyte function, the role of these cells on brain function and behavior during inflammation warrants investigation. In the present study we employed mice deficient in lymphocyte function and studied behavioral and inflammatory responses during challenge with bacterial lipopolysaccharides (LPS). Rag2−/− mice lacking mature lymphocytes were susceptible to death under sub-septic (5 mg/kg) doses of LPS and survived only to moderate (1 mg/kg) doses of LPS. Under these conditions, they displayed attenuated TNF-alpha responses and behavioral symptoms of sickness when compared with immunocompetent mice. Nevertheless, Rag2−/− mice had protracted motivational impairments after recovery from sickness suggesting a specific function for lymphocytes on the re-establishment of motivational states after activation of the innate immune system. The behavioral impairments in Rag2−/− mice were paralleled by an elevation in plasma corticosterone after behavioral tests. These results provide evidence that the absence of adaptive immunity may be associated with emotional deficits during inflammation and suggest that depressive states associated with medical illness may be mediated in part by impaired lymphocyte responses.

Kynurenic acid, a metabolite of the kynurenine pathway of tryptophan degradation, acts as an endogenous antagonist of alpha7 nicotinic and NMDA receptors and is implicated in a number of neurophysiological and neuropathological processes including cognition and neurodegenerative events. Therefore, kynurenine aminotransferase II (KAT II/AADAT), the enzyme responsible for the formation of the majority of neuroactive kynurenic acid in the brain, has prompted significant interest. Using immunohistochemistry, this enzyme was localized primarily in astrocytes throughout the adult rat brain, but detailed neuroanatomical studies are lacking. Here, we employed quantitative in situ hybridization to analyze the relative expression of KAT II mRNA in the brain of rats under normal conditions and 6 h after the administration of lipopolysaccharides (LPSs). Specific hybridization signals for KAT II were detected, with the highest expression in the subventricular zone (SVZ), the rostral migratory stream and the floor of the third ventricle followed by the corpus callosum and the hippocampus. This pattern of mRNA expression was paralleled by differential protein expression, determined by serial dilutions of antibodies (up to 1:1 million), and was confirmed to be primarily astrocytic in nature. The mRNA signal in the SVZ and the hippocampus was substantially increased by the LPS treatment without detectable changes elsewhere. These results demonstrate that KAT II is expressed in the rat brain in a region-specific manner and that gene expression is sensitive to inflammatory processes. This suggests an unrecognized role for kynurenic acid in the brain’s germinal zones.

Background The Stanford Anesthesia Teaching Scholars Program was launched in 2007 to further pedagogic training of faculty and improve residency education. Objectives The goals of this article are to describe the program intervention and improvements made based on participant feedback, summarize the characteristics of the faculty enrolled and projects undertaken, and report on program outcomes tracked to date. Intervention The Teaching Scholars Program housed within the Department of Anesthesia supports faculty in these areas: (1) attending education-related meetings; (2) engaging in a monthly seminar on core topics paired with independent study reading; and (3) undertaking a project to improve resident education. Structured interviews with all graduates (n = 19; 47% women) were conducted using a pilot-tested questionnaire. Results A total of 15 of 19 Scholars (79%) were instructors/assistant professors. Sixteen Scholars (84%) attended an off-site education meeting. The Scholars pursued a variety of projects, including curriculum (53%), teaching (26%), administration (11%), assessment (5%), and advising/mentoring (5%). Projects were fully completed by 13 of 19 participants (68%), and 12 of 19 projects (63%) are currently integrated into the residency. Completed projects were published/presented at conferences by 4 of 13 participants (31%), and education grants were received by 3 of 19 participants (16%). Conclusions This is the first description of a faculty development (education) program in an anesthesiology department. The program has been well accepted by participants and resulted in increased educational products, some of which have become a permanent part of the residency curriculum. This educational innovation can be replicated in other departments of anesthesiology provided that funding is available for faculty time and meeting expenses.

Background: Neuroinflammatory processes are increasingly believed to participate in the pathophysiology of a number of major psychiatric diseases, including depression. Immune activation stimulates the conversion of the amino acid tryptophan to kynurenine, leading to the formation of neuroactive metabolites, such as quinolinic acid and kynurenic acid. These compounds affect glutamatergic neurotransmission, which plays a prominent role in depressive pathology. Increased tryptophan degradation along the kynurenine pathway (KP) has been proposed to contribute to disease etiology. Methods: We used postmortem brain tissue from the ventrolateral prefrontal cortex (VLPFC) to assess tissue levels of tryptophan and KP metabolites, the expression of several KP enzymes and a series of cytokines as well as tissue pathology, including microglial activation. Tissue samples came from nonpsychiatric controls (n = 36) and individuals with depressive disorder not otherwise specified (DD-NOS, n = 45) who died of natural causes, homicide, accident, or suicide. Results: We found a reduction in the enzymatic conversion of tryptophan to kynurenine, determined using the kynurenine:tryptophan ratio, and reduced messenger RNA expression of the enzymes indoleamine-2,3-dioxygenase 1 and 2 and tryptophan-2,3-dioxygenase in depressed individuals irrespective of the cause of death. These findings correlated with reductions in the expression of several cytokines, including interferon-γ and tumour necrosis factor-α. Notably, quinolinic acid levels were also lower in depressed individuals than controls. Limitations: Information on the use of antidepressants and other psychotropic medications was insufficient for statistical comparisons. Conclusion: Contrary to expectations, the present results indicate that depression, in the absence of medical illness or an overt inflammatory process, is associated with compromised, rather than increased, KP metabolism in the VLPFC.

Down Syndrome (DS), a genetic disease caused by a triplication of chromosome 21, is characterized by increased markers of oxidative stress. In addition to cognitive defects, patients with DS also display hematologic disorders and increased incidence of infections and leukemia. Using the Ts65Dn mouse model of DS, the goal of this study was to examine hematopoietic stem and lymphoid progenitor cell function in DS.Analysis of hematopoietic progenitor populations showed that Ts65Dn mice possessed fewer functional hematopoietic stem cells and a significantly decreased percentage of bone marrow lymphoid progenitors. Increased reactive oxygen species and markers of oxidative stress were detected in hematopoietic stem cell populations and were associated with a loss of quiescence. Bone marrow progenitor populations expressed diminished levels of the IL-7Rα chain, which was associated with decreased proliferation and increased apoptosis. Modulating oxidative stress in vitro suggested that oxidative stress selectively leads to decreased IL-7Rα expression, and inhibits the survival of IL-7Rα-expressing hematopoietic progenitors, potentially linking increased reactive oxygen species and immunopathology.The study results identify a link between oxidative stress and diminished IL-7Rα expression and function. Further, the data suggest that this decrease in IL-7Rα is associated with defective hematopoietic development in Down Syndrome.The data suggest that hematopoietic stem and lymphoid progenitor cell defects underlie immune dysfunction in DS and that increased oxidative stress and reduced cytokine signaling may alter hematologic development in Ts65Dn mice.

Parkinson’s disease (PD) is classically defined as a motor disorder resulting from decreased dopamine production in the basal ganglia circuit. In an attempt to better diagnose and treat PD before the onset of severe motor dysfunction, recent attention has focused on the early, non-motor symptoms, which include but are not limited to sleep disorders such as excessive daytime sleepiness (EDS) and REM behavioral disorder (RBD). However, few animal models have been able to replicate both the motor and non-motor symptoms of PD. Here, we present a progressive rat model of parkinsonism that displays disturbances in sleep/wake patterns. Epidemiological studies elucidated a link between the Guamanian variant of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) and the consumption of flour made from the washed seeds of the plant Cycas micronesica (cycad). Our study examined the effects of prolonged cycad consumption on sleep/wake activity in male, Sprague–Dawley rats. Cycad-fed rats exhibited an increase in length and/or number of bouts of rapid eye movement (REM) sleep and Non-REM (NREM) sleep at the expense of wakefulness during the active period when compared to control rats. This hypersomnolent behavior suggests an inability to maintain arousal. In addition, cycad-fed rats had significantly fewer orexin cells in the hypothalamus. Our results reveal a novel rodent model of parkinsonism that includes an EDS-like syndrome that may be associated with a dysregulation of orexin neurons. Further characterization of this early, non-motor symptom, may provide potential therapeutic interventions in the treatment of PD.

Exposure to a number of drugs, chemicals, or environmental factors can cause parkinsonism. Epidemiologic evidence supports a causal link between the consumption of flour made from the washed seeds of the plant Cycas micronesica by the Chamorro population of Guam and the development of amyotrophic lateral sclerosis/parkinsonism dementia complex.We now report that consumption of washed cycad flour pellets by Sprague-Dawley male rats induces progressive parkinsonism.Cycad-fed rats displayed motor abnormalities after 2 to 3 months of feeding such as spontaneous unilateral rotation, shuffling gait, and stereotypy. Histological and biochemical examination of brains from cycad-fed rats revealed an initial decrease in the levels of dopamine and its metabolites in the striatum (STR), followed by neurodegeneration of dopaminergic (DAergic) cell bodies in the substantia nigra (SN) pars compacta (SNc). alpha-Synuclein (alpha-syn; proteinase K-resistant) and ubiquitin aggregates were found in the DAergic neurons of the SNc and neurites in the STR. In addition, we identified alpha-syn aggregates in neurons of the locus coeruleus and cingulate cortex. No loss of motor neurons in the spinal cord was found after chronic consumption of cycad flour. In an organotypic slice culture of the rat SN and the striatum, an organic extract of cycad causes a selective loss of dopamine neurons and alpha-syn aggregates in the SN.Cycad-fed rats exhibit progressive behavioral, biochemical, and histological hallmarks of parkinsonism, coupled with a lack of fatality.

Diffusion Tensor magnetic resonance imaging and computational neuroanatomy are used to quantify postnatal developmental patterns of C57BL/6J mouse brain. Changes in neuronal organization and myelination occurring as the brain matures into adulthood are examined, and a normative baseline is developed, against which transgenic mice may be compared in genotype–phenotype studies. In early postnatal days, gray matter–based cortical and hippocampal structures exhibit high water diffusion anisotropy, presumably reflecting the radial neuronal organization. Anisotropy drops rapidly within a week, indicating that the underlying brain tissue becomes more isotropic in orientation, possibly due to formation of a complex randomly intertwined web of dendrites. Gradual white matter anisotropy increase implies progressively more organized axonal pathways, likely reflecting the myelination of axons forming tightly packed fiber bundles. In contrast to the spatially complex pattern of tissue maturation, volumetric growth is somewhat uniform, with the cortex and the cerebellum exhibiting slightly more pronounced growth. Temporally, structural growth rates demonstrate an initial rapid volumetric increase in most structures, gradually tapering off to a steady state by about 20 days. Fiber maturation reaches steady state in about 10 days for the cortex, to 30–40 days for the corpus callosum, the hippocampus, and the internal and external capsules.

Accumulating evidence has shown that adaptive immune cells are capable of modulating behavior and cognition via interactions with the brain and central nervous system elements. Nevertheless, since a vast majority of these studies were conducted in adult, constitutive knockout models of immune deficiency, it raises the question of whether compensatory mechanisms associated with development in a lymphopenic environment may explain some of the behavioral observations. To address this, neonate Rag2-/- (P2) mice were reconstituted with whole lymphocytes (ReconWL) derived from GFP+ wild type donors. Starting at 5 weeks of age (mid-adolescence) ReconWL, saline injected Rag2-/- and C57BL/6 J control mice underwent a series of behavioral tests including the open field, social interaction and sucrose preference tests. Then at 12 weeks (young adult) they were evaluated in the Morris Water Maze. Remarkably, reconstituted mice showed changes in almost all aspects that were assessed. Perhaps most notable however, was the complete rescue of impaired social behavior displayed by non-reconstituted Rag2-/- mice. While Rag2-/- mice preferred a non-social area and spent significantly less time with a conspecific mouse, ReconWL mice were comparable to wild type mice. Additionally, consistent with previous reports, Rag2-/- mice had deficits in reversal learning in the MWM that were rescued by reconstitution. These findings support a role for lymphocytes in modulating a spectrum of behavioral and cognitive processes across the lifespan.

Significant evidence suggests that exposure to traumatic and/or acute stress in both mice and humans results in compromised immune function that in turn may affect associated brain processes. Additionally, recent studies in mouse models of immune deficiency have suggested that adaptive immunity may play a role during traumatic stress exposure and that impairments in lymphocyte function may contribute to increased susceptibility to various psychogenic stressors. However, rodent studies on the relationship between maladaptive stress responses and lymphocyte deficiency have been complicated by the fact that genetic manipulations in these models may also result in changes in CNS function due to the expression of targeted genes in tissues other than lymphocytes, including the brain. To address these issues we utilized mice with a deletion of recombination-activating gene 2 (Rag2), which has no confirmed expression in the CNS; thus, its loss should result in the absence of mature lymphocytes without altering CNS function directly. Stress responsiveness of immune deficient Rag2(-/-) mice on a BALB/c background was evaluated in three different paradigms: predator odor exposure (POE), fear conditioning (FC) and learned helplessness (LH). These models are often used to study different aspects of stress responsiveness after the exposure to an acute stressor. In addition, immunoblot analysis was used to assess hippocampal BDNF expression under both stressed and non-stressed conditions. Subsequent to POE, Rag2(-/-) mice exhibited a reduced acoustic startle response compared to BALB/c mice; no significant differences in behavior were observed in either FC or LH. Furthermore, analysis of hippocampal BDNF indicated that Rag2(-/-) mice have elevated levels of the mature form of BDNF compared to BALB/c mice. Results from our studies suggest that the absence of mature lymphocytes is associated with increased resilience to stress exposure in the POE and does not affect behavioral responses in the FC and LH paradigms. These findings indicate that lymphocytes play a specific role in stress responsiveness dependent upon the type, nature and intensity of the stressor.

In addition to archetypal cognitive defects, Down syndrome (DS) is characterized by altered lymphocyte development and function, including premature thymic involution and increased incidence of infections. However, the potential mechanisms for these changes have not been fully elucidated. The current study used the Ts65Dn mouse model of DS to assess deficiencies in T-cell development and possible molecular alterations. Ts65Dn mice exhibited premature thymic involution and a threefold to fourfold decrease in the number and proportion of immature, double-negative thymocyte progenitors. In addition, there were twofold fewer double-positive and CD4 single-positive thymocytes in Ts65Dn thymuses. Reflecting this deficient thymic function, there were fewer naive T cells in the spleen and polyclonal stimulation of peripheral T cells exhibited a marked reduction in proliferation, suggesting a senescent phenotype. In contrast, B-cell progenitors were unchanged in the bone marrow of Ts65Dn mice, but in the spleen, there were decreased transitional and follicular B cells and these cells proliferated less upon antigen receptor stimulus but not in response to lipopolysaccharide. As a potential mechanism for diminished thymic function, immature thymocyte populations expressed diminished levels of the cytokine receptor interleukin-7Rα, which was associated with decreased proliferation and increased apoptosis. Increased oxidative stress and inhibition of the Notch pathway were identified as possible mediators of decreased interleukin-7Rα expression in Ts65Dn mice. The data suggest that immature thymocyte defects underlie immune dysfunction in DS and that increased oxidative stress and reduced cytokine signalling may alter lymphocyte development in Ts65Dn mice.

Brain derived neurotrophic factor (BDNF) is ubiquitously expressed throughout the central nervous system and is vital for the maintenance of neuronal survival and function. Recent studies examining mRNA levels and total BDNF expression have suggested that the adaptive immune system may contribute to brain homeostasis and neuronal function via modulation of this neurotrophin. Taking into consideration BDNF processing and the opposing roles of pro-BDNF and mature BDNF on synaptic plasticity, we evaluated levels of both BDNF forms in the hippocampus of wild type C57Bl/6 and Rag2-/- mice that underwent stress exposure in the learned helplessness paradigm. Using this model, in conjunction with the reconstitution of Rag2-/- mice with naive T cells, we have shown that T cells modulate BDNF levels and the ratio of mature BDNF to pro-BDNF following exposure to inescapable stress. Compared to wild type mice, Rag2-/- mice displayed elevated levels of pro- and mature BDNF, concurrent with an increase in the mature:pro-BDNF ratio, two hours after stress exposure. Furthermore, adoptive transfer of naive T cells was sufficient to block this increase. Evaluation of BDNF levels after subsequent exposure to escapable stress did not reveal any differences in expression. These findings suggest that T cells modulate hippocampal BDNF levels as part of the development of adaptive processes in response to stress.

The Rag2-/- mouse model of T cell deficiency is a useful tool for the study of behaviors associated with T cell function. We have previously shown that Rag2-/- mice on a BALB/c background are more resistant to developing post-traumatic anxiety using the model of exposure to predator odor (POE). The objectives of the present studies were two-fold: first, to determine if behavioral differences in the POE model were also present in Rag2-/- mice on a C57Bl/6 background and second, to determine if these behavioral differences were dependent on T cells. Wild type (WT) and Rag2-/- mice on C57Bl/6 background and Rag2-/- mice reconstituted with naive T cells were compared in the POE model. Mice were exposed to cat odor for 10 minutes and tested 7 days later in the elevated plus maze (EPM) test followed by the acoustic startle response (ASR) one day later. Compared to mice on a BALB/c background, WT and Rag2-/- mice showed consistent behavioral phenotypes in the EPM and ASR, with Rag2-/- mice displaying decreased ASR reactivity with respect to WT and no differences in the EPM. Reconstitution with T cells modified behavioral responses in the EPM, but did not affect ASR responses. These results suggest that T cells may affect stress responsiveness, independent of genotype, by functional as well as developmental effects in an endophenotype-specific manner.

The Ts65Dn mouse, an adult model of Down syndrome displays behavioral deficits consistent with a dysfunctional hippocampus, similar to that seen with DS. In looking for mechanisms underlying these performance deficits, we have assessed adult neurogenesis in the dentate gyrus of Ts65Dn. Under untreated conditions, Ts65Dn mice (2-5 months old) showed markedly fewer BrdU-labeled cells than euploid animals. Chronic antidepressant treatment for over 3 weeks with the serotonin selective reuptake inhibitor, fluoxetine, increased neurogenesis in the Ts65Dn to comparable levels seen in the euploid by augmenting both proliferation and survival of BrdU-labeled cells in the subgranular layer and granule cell layer of the hippocampus, respectively.

Inflammatory diseases are highly associated with affective disorders including depression and anxiety disorders. While the role of the innate immune system on emotion has been extensively studied, the role of adaptive immunity is less understood. Considering that chronic inflammatory conditions are maintained largely by maladaptive lymphocyte function, the role of these cells on brain function and behavior during inflammation warrants investigation. In the present study we employed mice deficient on lymphocyte function by deletion of the RAG2 gene necessary for T and B cell receptor re-arrangement. Their behavioral and inflammatory responses during challenge with bacterial lipopolysaccharides (LPS) were compared with immune competent wild type mice. Mice deficient in lymphocytes were susceptible to death under sub-septic doses of LPS and survived only to low doses of LPS. Under these conditions, they displayed an attenuated inflammatory response that was related with a faster recovery from sickness. Nevertheless, these mice displayed increased emotional disturbances after recovery from sickness suggesting a specific function for lymphocytes on the re-establishment of motivational states after activation of the innate immune system. These results provide evidence that a defective lymphocyte response is associated with emotional deficits during inflammation and suggest that emotional states associated with medical illness may be influenced by the activity of lymphocytes.